Error occured in deployment step 'retract solution' cannot start service SPUserCodeV4 on this computer

I got this error when I tried to deploy a WebPart created using VS 2010 and Sharepoint 2010.

Solution

1. Go to Central Administration

2. Open "System Settings"

3. Open "Manage services on server"

4. Locate the service "Microsoft SharePoint Foundation Sandboxed Code Service"

5. Start the service "Microsoft SharePoint Foundation Sandboxed Code Service"

Now try deploying the WebPart and it will deploy successfully.